An assessment of probabilistic seismic hazard for the cities in Southwest Turkey using historical and instrumental earthquake catalogs

The tectonically active southwestern part of Turkey is dominated by the Aegean Extensional Province. The primary aim of this study is to evaluate the seismic hazard for the cities in SW Turkey using a probabilistic approach. As part of this research, a new earthquake database based on a unified moment magnitude scale was created, which contains shallow crustal earthquakes from 1000 to 2021. The catalog's foreshock and aftershock occurrences were excluded depending on the space–time windows, and a catalog completeness analysis was conducted. The uncertainty in magnitude determination was taken into account. The seismic sources were defined as homogeneous area source zones, taking into consideration the active fault zones. The activity rate and the Gutenberg–Richter b parameter as earthquake hazard parameters for each seismic source have been evaluated by the Kijko–Smit maximum likelihood estimation method. An "efficacy test," which uses the average log likelihood value (LLH), was performed to find the suitable ground motion prediction equations for SW Turkey. The maximum magnitude (Mmax) of each seismic source was calculated based on the regional rupture characteristics and the Kijko–Sellevoll methods. Seismic hazard maps for SW Turkey were developed for Peak ground acceleration (PGA), spectral acceleration with periods of 0.2 and 1 s and for bedrock with a hazard level of 10% probability of exceedance in 50 years by using Geographical Information System software. Based on this study, the PGA values on the bedrock in SW Turkey range from 0.253 to 0.572 g. As part of this research, seismic hazard curves and uniform hazard spectrums were created for the settlement areas of the cities in SW Turkey. In addition to this PSHA, PGA values at the settlement areas with events at probable future rupture locations were estimated for different site amplification classes.